Subnational Population Estimates

1988:

Local Government Amendment Act No 3 provides for the constitution of 14 Regional Councils.

The regional council areas cover every territorial authority area in New Zealand with the exception of Chatham Islands County.

These replaced 22 Local Government Regions.

1 Nov 1989:

Local government reorganisation creates 74 Territorial Authority areas. These replaced 213 Local Authorities.

1 July 1992:

The number of regions increased to 16 following boundary reorganisation in the northern South Island.

1 Jan 2001:

Chatham Islands District became Chatham Islands Territory.

1 March 2004:

Tauranga District became Tauranga City.

March 2006:

Banks Peninsula District amalgamated with Christchurch City.

December 2008:

Statistics New Zealand adopted a new method for producing subnational population estimates by age group and sex.

This new method was used to revise subnational population estimates, at 30 June 2007 but did not affect the total population estimate at each subnational area.

1 Nov 2010:

A new unitary authority (the Auckland Council) became operational. Two districts (Rodney and Papakura) and four cities (North Shore, Waitakere, Auckland and Manukau) became part of the new Auckland Council area.

The Franklin District was divided between three territorial authority areas: Auckland, Hauraki District, and Waikato District.

2011:

Following the 2010/11 Canterbury earthquakes a number of additional data sources were used to assess subnational population change during the June 2011 year.

These data sources are described in Estimating local populations after the 2010/11 Canterbury earthquakes. (http://www.stats.govt.nz/browse_for_stats/population/estimates_and_projections/estimating-pop-after-chch-quakes-paper.aspx)

2011:

The regional council and territorial authority areas for the subnational population estimates at 30 June 1996 forward were rebased on boundaries at 1 July 2011.

2012:

Alternative data sources have been further utilised for subnational (regional councils, territorial authorities, and area unit) population estimates.

Primary Health Organisation enrolment data, electoral enrolments, and IR tax data.

Net migration at the 15–24 ages is partly determined by historical patterns. Some differences compared to the historical population estimates trends will occur in terms of geographic areas, by age groups and sex. However, these differences are minimal and should have low or no impact on our data users.

2013:

Publication of population estimates at area unit level has been brought forward to the same time as for estimates at territorial authority and Auckland local board areas and regional council areas. This is due to a new method being implemented for deriving the area unit estimates. It is fully data-driven, automatable, and more transparent, allowing users to more readily assess the limitations of the estimates at this level of geography.

2015:

Refined method used for area unit estimates to improve the accuracy of the age-sex estimates at area unit level.

2018:

Subnational population estimates published on new statistical geographies - statistical area 2 (SA2), and urban rural areas.

2019

A range of new data sources/methods were used for the 2019 subnational population estimates. These were derived with:

• interim outcomes-based international migration estimates to subnational areas

• projected internal migration rates, based on 2018 Census results

• an interim revised 2013-base 2018 estimates, consistent with the revised 2013-base national population estimates, taking subnational distributions from the 2018 Census into account.

2020 Population estimates 2019-2020 are revised to be consistent with the 2018-base national population estimates. 2014-2017 estimates are also revised to incorporate 2018-base estimated resident population.

Usage

Subnational population estimates are used in many administrative, statistical and research applications.

They are used by Government, regional planning authorities, local bodies, private organisations and individuals for determining future housing and other consumer needs, community amenities and social services at the subnational level. Subnational estimates of population also provide information on the supply of labour for employment and the growth of markets. Subnational estimates are available at 30 June; these estimates can be used as a proxy for mean year ended 31 December population estimates.

Limitations of subnational estimates

Population estimates give the best available measure of the size and age-sex composition of the population usually living in an area. However, uncertainty is inherent in the estimation process.

Stats NZ produces subnational (territorial authority and Auckland local board areas) population estimates using a component methodology, where estimates of the components of population change (births, deaths, and migration) are used to update a base population.

Subnational population estimates are constrained to the national estimates and, therefore, the quality of subnational estimates is affected by the quality of the components of national estimates. There are also some additional uncertainties that arise when estimating the components of population change at the subnational level, particularly estimating net migration (external/international and internal migration combined) for subnational areas. Due to these factors, uncertainty generally increases with reference dates further from the base (starting-point). Uncertainty also increases as population estimates are broken down by age, sex, and geographic area.

It is important to note that population estimates for small geographic areas (eg SA2s) are more uncertain than estimates released at broader geographic levels because information on external and internal migration is often not readily available or of insufficient quality at the low geographic level and localised developments (eg greenfield subdivisions) can have a significant impact on the net migration patterns and population structure of SA2s, but this impact can be difficult to identify.

Data accuracy

It is not possible to ascertain the accuracy of current post-censal estimates as no independent authoritative measure of the resident population exists. Since 2013, Stats NZ has implemented a number of changes to its estimation methods aimed at improving the accuracy of population estimates by refining methods for using existing data sources. New data sources have also been explored for future improvements, see Experimental series of internal migration estimates using linked administrative data for details.

The periodic Census of Population and Dwellings remains the cornerstone of population statistics in New Zealand. Following the 2018 Census it we will be possible to derive updated estimates of the population, to assess the accuracy of estimates since 2013, and to revise estimates where necessary. from 30 June 2013 onward.

See data collections - methodology for further information.

Statistics New Zealand, Ministry of Education, Ministry of Health, Government Planners/Local Body Planners, researchers

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